Currently, the mainstream touch control technologies include capacitive touch sensing and resistive touch sensing, of which the resistive touch sensing technology may be further divided into four-wire resistive touch sensing, five-wire resistive touch sensing and eight-wire resistive touch sensing. A resistive touch sensor is constructed mainly by an indium tin oxide (ITO) glass plate, an ITO thin film, and a spacer for separating the ITO glass plate from the ITO thin film. When a finger, a stylus or another medium touches on a resistive touch sensor, it will cause a short-circuit between the ITO glass plate and the ITO thin film at the touch point and thereby induce a voltage drop, so that the touch point can be sensed responsive to the voltage drop. For capacitive touch input, it may be classified into surface capacitance touchpad module and projected capacitance touchpad module. A capacitive touchpad module may include an ITO, a membrane, a printed circuit board (PCB), or a flexible printed circuit (FPC) board. When a finger or a conductor touches on a capacitive touchpad module, it will cause a capacitance variation at the touch point and thereby the touch point can be sensed accordingly.
As the capacitive touch sensing does not rely on deformation of a sensor to sense the touch point, it is impossible to use a stylus with a capacitive touchpad module, as does for the resistive touch sensing. Even if the tip of a stylus were replaced with a conductor, it would still be impossible for the stylus to induce a sufficient capacitance variation of a trace of the capacitive touchpad module because of the too-small size of the tip. Although this problem may be solved by enlarging the tip of a stylus, the tip, after being enlarged, would become as thick as a finger, which is unfavorable for such applications as handwriting recognition and drawing in a small-sized capacitive touchpad module. Moreover, capacitive touch sensors used in cell phones or notebook computers are usually provided with a plurality of virtual buttons, which are made to be very small and located very close to each other, so it is impossible to correctly click such virtual buttons by use of a stylus having a large tip.
Therefore, it is desired a novel stylus having a small tip for capacitive touch input.